Sediment removal from the bottom of natural and artificial bodies of water falls broadly into one of two camps, i.e., navigational and environmental. The primary purpose of the former is to create and/or maintain bodies of water open for navigation while the primary purpose of the latter is to remove sediment considered a threat to public health from a body of water.
Contaminated sediments can be removed by a number of different methods. One method is mechanical dredging using a modified clamshell bucket. These buckets use positioning devices to locate and extract sediment one bucket at a time. This method produces good results, but can be and often is time, equipment and manpower intensive.
Another method is hydraulic dredging which is commonly used in areas of shallow water. This is a more efficient means of removing material, but it often requires multiple passes to achieve designated decontamination levels. This method typically employs a cutter head or a horizontal auger to aid in the removal of these sediments. The cutter head dredge has advantages over the auger dredge due to its ability to follow contours when possessing articulating and swinging capabilities. This is an efficient and effective way to remove material, eliminating the need for dredge swing line anchors.
The horizontal auger also has its strengths. The auger can cover a wide swath of area at any given time, and to some degree, follow contours. However, large materials and debris can be very problematic for an auger due to the large distance materials must travel from the end of the auger to the suction pipe.
Both the cutter head and horizontal auger have difficulties with reducing the turbidity produced through dredging because to remove intended sediments, the sediments must first be agitated.